Characteristics of Life

Conventional Definitions of Life

• Organization: Composed of one or more cells, the basic units of life.
• Reproduction: Ability to produce new organisms.
• Metabolism: Undergoes chemical processes for life maintenance.
  • Catabolism: Breakdown of substances to provide energy.
  • Anabolism: Synthesis of substances using energy.
• Growth: Maintains a higher rate of building up than breaking down, progressing from simpler to more complex states.
• Homeostasis: Regulates internal environment to maintain constant conditions, such as sweating to reduce temperature or shivering to increase temperature.
• Response to Stimuli: Ability to react to stimuli.
• Adaptation: Ability to respond to environmental changes over time.

Other Proposed Features of Life

• Carbon-Containing: Carbon is the fundamental element of life on Earth.
• Reliance on Water: Water is essential for all life forms.
• Genetic Information: Uses DNA and RNA to store an organism's blueprint.

What is a Molecule

• Molecule: Smallest particle retaining a substance's properties, composed of one or more atoms.
• Atom: Smallest particle of an element retaining its chemical properties.

Molecular Characteristics of Life

• Laws of Thermodynamics: Life obeys these fundamental laws.
  • 1st Law: Energy cannot be created or destroyed, only changed.
  • 2nd Law: All processes increase entropy (disorder). Larger molecules have less entropy than smaller molecules.
• ATP: Common energy currency of life in biochemistry.
• Biological Molecules: Life is made of similar biological molecules (large and small). These include proteins, lipids, carbohydrates, and nucleic acids.

What is a Nutrient

• Nutrient: Any substance with nutritional value, providing energy and building blocks for maintenance, growth, and repair.
• Essential Nutrients: Some can be synthesized, others are not and must be obtained from food.

Micronutrients vs Macronutrients

• Micronutrient: Required in small amounts (vitamins, microminerals).
• Macronutrient: Required in large amounts (carbohydrates, proteins, lipids).

Vitamins

• Role: Act as cofactors for enzymes, organic molecules loosely bound to enzymes during reactions.
• Source: Obtained from food.

Nucleic Acids

• Role: Essential for maintaining, growing, and repairing DNA and RNA.

RNA

• Role: Messenger carrying instructions from DNA.
• Structure: Single-stranded and complementary to DNA, using uracil instead of thymine.
• Components: Ribonucleotides build new RNA.

Hydrocarbon Nomenclature

• Hydrocarbons: Compounds containing only hydrogen and carbon.
• Alkane: Carbon-carbon single bonds.
• Alkene: Carbon-carbon double bonds.
• Alkyne: Carbon-carbon triple bonds.

Methods of Drawing Hydrocarbons

• Structural: Straight lines represent bonds.
• Condensed: Combines hydrogen with carbons.
• Skeletal: Intersections represent carbon atoms.

Naming Linear Hydrocarbons

• Prefixes: Meth (1), Eth (2), Prop (3), But (4), Pent (5), Hex (6), Hept (7), Oct (8), Non (9), Dec (10), etc.

Atomic Structure

• Nucleus: Central part containing protons and neutrons (each with 1 atomic mass unit).
• Electrons: Negatively charged particles orbiting the nucleus (essentially zero mass).
• Orbitals: Electron orbitals are filled from inside to outside. The first shell holds 2 electrons, and the second and third hold 8 each.

Bond Formation by Atoms

• Bonds: Number of bonds formed depends on the number of electrons needed for a full outer orbital.

Types of Chemical Bonds

• Intramolecular: Bonds within a molecule (covalent/ionic).
• Intermolecular: Bonds between molecules (hydrogen/Van der Waals/hydrophobic).

Relative Chemical Bond Strengths

• Intramolecular: Stronger, requiring more energy to form and release more energy when broken.
• Intermolecular: Weaker.

Covalent Bonds

• Formation: Sharing of electron pairs between atoms.
• Characteristics: Stable, strong bonds.

Ionic Bonds

• Formation: Transfer of electrons between atoms.
• Characteristics: One atom loses electrons and another gains them.

Hydrogen Bonds

• Formation: Attraction between hydrogen and electronegative atoms (e.g., oxygen).
• Strength: Significantly weaker than covalent bonds.

Van Der Waals Forces

• Formation: Electrostatic attraction between temporarily induced dipoles in molecules.
• Strength: Weak, temporary attractions.

Hydrophobic Force

• Formation: Non-polar molecules tend to cluster together to avoid water.

Electronegativity and Bond Type

• Electronegativity: Atom's ability to attract electrons. High electronegativity=strong attraction, low electronegativity= weak attraction.
• Bond Polarity Spectrum: Non-polar, polar covalent to ionic, based on electronegativity difference.

Polar Bond vs Polar Molecule

• Molecular Polarity: Sum of all bonds' polarity.
• Polar Molecule: The characteristics of the whole molecule are polar

Water

• Polarity: Oxygen is more electronegative than hydrogen, leading to partial charges.

Solubility and Polarity

• Polar/polar: Dissolve in each other.
• Non-polar/non-polar: Dissolve in each other.
• Polar/non-polar: Do not dissolve.

Water and pH

• Ionization: Water molecules can dissociate into ions.

Acids and Bases

• Acids: Proton donors.
• Bases: Proton acceptors.

Acids and Bases in the Body

• pH Balance: Essential for biological function.
• Blood pH: Maintained within a narrow range (7.35-7.45).

Isomers

• Definition: Molecules with the same chemical formula but different atom arrangements.
  • Structural: Different bonding arrangements.
  • Spatial: Same bonding arrangement, different spatial arrangement.

Platin (Cisplatin and Transplatin)

• Cisplatin: Prevents cancer cell replication by binding to DNA.
• Transplatin: Ineffective due to rapid breakdown.

Energy

• Chemical Energy: Stored in atomic bonds. Release of energy when bonds break.

Enthalpy (ΔH)

• Definition: Heat content of a molecule.
• ΔH = Final–Initial: Heat lost or gained.
• Exothermic (-ΔH): Heat released to surroundings.
• Endothermic (+ΔH): Heat absorbed from surroundings.

Spontaneous Reaction (-ΔG)

• Spontaneity: Reaction proceeds without external input of energy, reaction loses heat.

Entropy (ΔS)

• Definition: Disorder of molecules in a system.
• ΔS = Final–Initial: Disorder changes.
  • Arrangements: More disordered=greater entropy.
  • Number of Molecules: More molecules=greater entropy.
  • Motion of Molecules: More motion=greater entropy

Gibbs Free Energy (ΔG)

• Definition: Combines enthalpy and entropy.
• ΔG = ΔH - TΔS / ΔG = GFinal-GInitial: Maximum energy available for work.
• Exergonic (-ΔG): Release energy, spontaneous.
• Endergonic (+ΔG): Requires energy input, non-spontaneous.

Conditions Favoring Exergonic Reactions

• Favored: Reactions that lose heat and gain entropy.

Delta G vs Delta G॰

• ΔG: Actual free-energy change in a reaction.
• ΔG°: Standard free-energy change under controlled conditions.

Energy in Food - Gross Energy

• Definition: Total energy in food.

Non-Usable Energy

• Types: Fecal, urinary, gaseous.

Usable Energy (Metabolic Energy)

• Definition: Energy available for work (growth, repair, reproduction).

Energy Out (Energy Expenditure)

• Factors: Basal metabolic rate (BMR), thermic effect of food (TEF), activity level.

3 Factors Affecting Obesity Epidemic

• Fast food intake.
• Added sugar intake.
• Large portion sizes.

Amino Acids

• Definition: Building blocks of proteins.
• Types: 20 standard amino acids.
  • Essential: Must be obtained from diet.

Protein Peptides

• Dipeptide: 2 amino acids.
• Tripeptide: 3 amino acids.
• Oligopeptide: 4-50 amino acids.
• Linked by peptide bonds.

Protein Polymers

• Polypeptide: >50 amino acids, <100 amino acids.
• Linear: Linked by peptide bonds.

Biological Proteins

• Size: Hundreds to thousands of amino acids.
• Structure: Complex, often globular.
• Functionality: Folded structure crucial for function.

Complete vs Incomplete Proteins

• Complete: Contains all essential amino acids (animal proteins).
• Incomplete: Lacks some essential amino acids (plant proteins).

Protein Structure

• Primary (1°): Amino acid sequence.
• Secondary (2°): Arrangement of amino acids via hydrogen bonds (α-helices, β-sheets).
  • α-helix: Coiled structure.
  • β-sheet: Sheet-like structure.
• Tertiary (3°): Folding of 2° structures into a compact 3D shape via interactions between side chains.
  • Forces: Disulfide bonds, hydrogen bonds, salt bridges, hydrophobic interactions.
• Quaternary (4°): Association of multiple polypeptide subunits.

Protein Denaturation

• Definition: Disruption of 2°, 3°, and 4° structures.
• Causes: Heating, acid/base treatment, organic compounds, heavy metals.

Dynamic vs. Static Proteins

• Dynamic: Mobile (transport, hormones, enzymes).
• Static: Fixed (structural proteins).

Serum Albumins

• Function: Maintain osmotic pressure, transport nonpolar substances.

Globulins

• Function: Transport, binding, eliminating foreign particles.

Hemoglobin

• Location: Red blood cells.
• Structure: 4 globin protein subunits and heme prosthetic groups.

Myoglobin

• Location: Muscle cells.
• Detection: In blood after muscle damage.

Insulin

• Role: Regulates blood glucose levels, signaling glucose uptake.

Thyroid Hormones (T3 & T4)

• Role: Metabolic regulation, feedback inhibition.

Somatropin (Human Growth Hormone)

• Role: Stimulates growth and cell metabolism.

Collagen

• Structure: Three strands of procollagen linked.

Elastin

• Structure: Multiple tropoelastin molecules linked.

Proteoglycans

• Location: Various tissues.

Fibronectin

• Role: Crosslinking ECM proteins.

Actin and Myosin

• Role: Muscle contraction.

Dietary Proteins

• Importance: Essential amino acids must be obtained from diet.